In each row of the diagram, the sum of the left and right hand digits, minus the central digit is always 8.

Divide the circle, horizontally and vertically, to give 4 quarters.

The sum of the numbers in the segments of each quarter equals 11.

Working through the diagram in rows, and reading each row as a whole number, the diagram represents a subtraction sum : 203 - 7 = 196

Moving from left to right, add 6 to the first number to get the next one along, then 8, 10 and 12 to complete the sequence.

Starting with the top left number, and working down one row at a time, alternating between left and right, double the number each time.

Repeat this sequence, starting with the top right number.